1. Technical Field
The present invention relates to an image display apparatus and in particular, to a technique of an image display apparatus that displays an image using a laser beam.
2. Related Art
A technique of using a laser light source as a light source of an image display apparatus, such as a projector, has been recently proposed. As compared with a UHP lamp that has been used as a light source of a projector in the related art, the laser light source is advantageous in high color reproducibility, instant lighting, a long life, and the like. Moreover, since loss of energy is low and luminous efficiency is high compared with the UHP lamp, it is also considered that the laser light source is effective in reducing the power consumption of the image display apparatus.
An example of an image display apparatus that uses a laser light source includes an image display apparatus that displays an image by scanning a laser beam, which is coherent light, with a light scanning device and making the laser beam irradiated onto an irradiated surface, such as a screen. When the laser beam is irradiated onto the irradiated surface, an interference pattern called a speckle pattern in which bright points and dark points are randomly distributed may appear.
The speckle pattern is a dynamic brightness pattern (also called a speckle noise) occurring due to random interfere of light beams diffused at points of a diffused surface. Since the speckle pattern is recognized as fine particle shaped glare to human eyes, the speckle pattern greatly lowers the display quality of an image. For this reason, it is necessary to take measures against the speckle noise in case of using a laser light source.
In order to reduce the speckle noise, for example, International Publication No. 2005/078519 pamphlet proposes a technique of rocking an optical path of a laser beam irradiated onto an irradiated surface. In the technique proposed in International Publication No. 2005/078519 pamphlet, the speckle noise is reduced by shifting irradiated positions of laser beams on the irradiated surface by rocking of the optical path so that a plurality of speckle patterns are superimposed.
However, when the irradiated positions of laser beams on the irradiated surface are shifted, the image may be recognized as a vibrating image or a blurred image due to the shift. As a result, the display quality of the image may lower on the contrary.